[time-nuts] HP 5245L Question

paul swed paulswedb at gmail.com
Sat Jan 9 21:23:47 UTC 2010


Peter absolutely do-able. If the goal is to use the counter then any number
of divider latch and decoders will work. You do have to adjust the various
voltages to the transfer gate/latch and counters... They are -15V or +20 V.
But absolutely do-able. Additionally if you replace the whole bunch you have
to add a small switching supply +5V as an example to drive the leds and
logic. They make very small supplies these days.
So CRAZZZY reality. I have 4 HP 5360 computing counters. Worlds largest
calculator by the way. One of them was the basket case and there was a
screwball mod to adapt LEDS into it.
No documentation just nuts. Spent a ton of time trying to save it.
My solution for the 14 nixies was this.

The HP 5360 printer port had all the information and was working.
Ran that info to a SX28 basic very fast single chip processor (28pins)
attached to 2 Maxim display driver chips and purchased large yellow/orange 7
seg LEDs. (Color very close to nixies.)

Its a sweet arrangement and works very well. By the way since I have the
data I pump it all out a rs232 port as well at 38.4 Kb/s could go faster but
that seemed fine enough to me.

The hardest part was wiring the 7 seg LEDs 14 X 8-9 connections each is
about 150 solder joints. I do all point to point. So it turned out well and
everything fit right into the front bezzel like the original display.
The same trick would definitely work on the 5245/8 series of counters.
Good luck and it sure does not hurt to try.
Regards


On Sat, Jan 9, 2010 at 4:00 PM, <g4gjl at btopenworld.com> wrote:

> I read the recent comments on the HP5245L with interest. I have several of
> these excellent instruments and recently used one in anger, to repair a
> 20GHz Signal Generator (HP 70000 Series) for my employer, thus saving them
> circa £10000.
>
> My question is, has anyone experienced the deterioration of the photo
> cells, another early semiconductor device with somewhat less than a forty
> years life expectancy? These seem to fail randomly, and I guess it is also a
> hygroscopic problem.
> I wondered about replacing nixie tubes and associated drivers with 7
> segment LEDs in one of my (already hacked) units, to make it more reliable.
> I would use the BCD to drive the display, thus requiring a new interface
> board to be designed. I wonder if anyone else has considered such a radical
> remedy to the failing photocell problem?
>
>  In case anyone is wondering 'WHY BOTHER?', my defence is that I too have
> an extensive collection of the plug ins, extending the usefulness of the
> basic instrument way beyond my budget for more modern equivalent
> instruments.
>
> Hope this question is not considered too far off topic for this forum.
>
> Peter Worrall
> G4GJL
> London
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